import {
  Injectable,
  NestInterceptor,
  ExecutionContext,
  CallHandler,
} from '@nestjs/common';
import { DataResponse, MessageResponse } from 'common/http';
import { Observable } from 'rxjs';
import { catchError, map } from 'rxjs/operators';

@Injectable()
export class ResponseInterceptor<T> implements NestInterceptor<T, any> {
  intercept(_: ExecutionContext, next: CallHandler): Observable<any> {
    return next.handle().pipe(
      map((data) => {
        if (data instanceof MessageResponse) return data;
        else if (data instanceof DataResponse) return data;
        else if (typeof data === 'string') return new MessageResponse(data);
        return new DataResponse(data);
      }),
    );
  }
}

/* NOTE: How to access request
 *
  @Injectable()
  export class ResponseInterceptor<T> implements NestInterceptor<T, any> {
    intercept(context: ExecutionContext, next: CallHandler): Observable<any> {
      const req = context.switchToHttp().getRequest();
      req.userId = 'ram';
      return next.handle();
      // return next.handle().pipe(
      //   map((data) => {
      //     if (data instanceof MessageResponse) return data;
      //     else if (data instanceof DataResponse) return data;
      //     else if (typeof data === 'string') return new MessageResponse(data);
      //     return new DataResponse(data);
      //   }),
      // );
    }
  }

REQUEST
  ↓
Guards
  ↓
Interceptors (before)
  ↓
Pipes
  ↓
Controller method
  ↓
Interceptors (after)  ← YOU ARE HERE
  ↓
Response


3️⃣ What is next.handle() really?
next.handle(): Observable<T>


This is:

An RxJS stream of whatever the controller returns

Not the request

Not the response object

Just the return value
 * */